Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
  Case Tag  
Price  
Sales  
Tax %  
Raw Total  
Incl. Sales Tax  
Rounded  
to Penny  
Rounded  
to Nickel  
Rounded  
to Dime  
  Purchase #1 $193.88   10.660%   $214.5476   $214.55   $214.55   $214.50  
  Purchase #2 $164.99   11.662%   $184.2311   $184.23   $184.25   $184.20  
  Purchase #3 $140.51   8.689%   $152.7189   $152.72   $152.70   $152.70  
  Purchase #4 $24.71   7.578%   $26.5825   $26.58   $26.60   $26.60  
  Purchase #5 $231.37   9.537%   $253.4358   $253.44   $253.45   $253.40  
  Purchase #6 $154.39   8.846%   $168.0473   $168.05   $168.05   $168.00  
  Purchase #7 $193.88   4.764%   $203.1164   $203.12   $203.10   $203.10  
  7 purchase totals = $1,103.73       $1,202.6796   $1,202.69   $1,202.70   $1,202.50